Model a Mixer Chain

SimRF™ Equivalent Baseband software uses a baseband equivalent
model to simulate RF components in the time domain, as described in SimRF Equivalent Baseband Algorithms. The blockset only
models a band of frequencies around the carrier frequency of each
component; the frequency band is determined by the following parameters
of the corresponding Input Port block:

Reciprocal of the Sample time (s)

Center frequency (Hz)

When a mixer is present in a physical subsystem, it shifts the
carrier frequency of the signal. This shift affects the frequencies
that are used to create baseband equivalent model.

To illustrate how the mixer works, consider a typical RF mixer
chain that consists of the following components:

Direct Quadrature Upconverter

High-Power Amplifier

Channel

Low-Noise Amplifier

Downconverting Mixer

IF Filter

Direct Quadrature Downconverter

The following diagram shows these components and the band of
frequencies that are simulated for each component. The signals at
the input and output of the cascade are baseband complex. For the
cascade, the diagram shows the real passband frequencies that are
used to create the baseband-equivalent model, which is centered at
zero. For a detailed explanation of how to use the blockset to model
quadrature mixers, see Quadrature Mixers.